This invention relates to an X-ray photograph unit which simplifies photograph control procedures.
In an X-ray photograph unit, a tube voltage and tube current of the X-ray tube and the exposure time must be suitably set in accordance with an object to be photographed.
Heretofore, the X-ray photograph unit has been set to the optimum photographing conditions and actuated by operating a tube voltage regulator, a tube current regulator and an exposure time adjuster (hereinafter called "timer") with reference to a photograph table which exclusively illustrates the conditions for the X-ray photograph for the portion to be photographed such as the tube voltage and tube current of the X-ray tube and the exposure time.
In other words, the optimum photographing conditions must be selected by sorting out the three kinds of factors on the photograph table. This procedure is not only time-consuming but also involves a high possibility of selecting the wrong conditions. In the latter case, the photograph itself must be taken again and this is extremely undesirable in the aspect of the exposure of the subject to the radioactive rays.
In the conventional X-ray photograph unit, the X-ray projection time is controlled by means of the timer. If the timer gets out of order, therefore, it sometimes happens that the X-ray irradiation does not stop, thus leading to a remarkable increase in the dose of exposure of the subject to the X-rays and hence, is extremely undesirable from the viewpoint of medical safety. As for the X-ray photograph unit, on the other hand, the X-rays are continuously irradiated in such a case, though the photograph must be originally taken within a short period of time under the rated state. Accordingly, the X-ray tube becomes overloaded and overheated and is eventually damaged and broken.
The present invention is directed to provide an X-ray photograph unit which eliminates the abovementioned drawbacks of the prior art, enables to simplify and accurately carry out the photograph control procedures and prevents the continuation of the X-ray irradiation at the time of accident.